Limit-switch.



PATENTED MAY 21, 1907.

G. BAEHR.

LIMIT SWITCH.

APPLIOATION FILED NOV.3,1906.

3 SHEBTfi-SHEET 1.

INVENTOR H U u v m u u U y u u h H. u U \z u v v 0 -HmWE A-r-i-oRNzYS No. 854,015. YPATENTED MAY 21, 1907. G.BAEHR.

LIMIT SWITCH.

APPLICATION FILED NOV. s. 1906.

3 S'HEETSSHEET 2.

'r'ro anzvs.

No. 854,015. PATENTED MAY 21, 1901. .G. BAE'HR. LIMIT SWITCH;

1 APPLICATION FILED NOV. 3,1906.

3 SHEETS-SHEET K J m k wnfirm:mask-12.5 IMVENTQR 4%,, i /MVQm ATTQHNEYE UNITED STATES PATENT OFFICE.

GEORGE BAEHR, or MOKEESPORT, PENNSYEANIA, ASSIGNO i To ELECTRIC CONTROLLER AND SUPPLY COMPANY, or CLEVELAND, OHIO, A CORPO- RATION OF' OHIO.

LIMIT-SWITCH.

Patented May 2 1907'.

Application filed N vembere, 1906. Serial No- 341 ,91 8.

10- matically'li'miting the motion or travel of any'machine drivenfrom an electric motor. t has been particularly designed for opening the circuit of the hoisting motor on an eleotric' cranewhen the limlt of travel-is 15 reached, but it maybe otherwise used.

Referringto the drawings which form a part of this specification, Figure 1 is a diagrammatic view of a limit switcharranged 2 load approaches theup or high to open the circuit of the motor when the osition.

- Fig. 2 is a similarjview showingt e limit hswltch arrangedto open the motor circuit at either, end of the travel of the machine, but.

not at both ends. Fig. 3' is a similar view ayshowing the limit switch arranged to en the motorcircuit as both limits of trave of the mechanism are reached; Fig. 4 is a {view showin the '-mechanioal connections between my lmit switch mechanism and a 3o hoisting device. Fig. 5 is a section on the line 5-5 of Fig. 4.

--Referring to Fig. 1 it will be sup osed that the contact dlSk w of the switch rotates as shown by the'arrow\ and that the contro'ller'arm C'is thrown to the up posi-- tionso as to bridge the contacts (1' and e, and 'n and o. .Thecurrent then passes from the plus side. of theswitch K throughthe line a, the terminal g tothe controller contact 6,

4olthe cross-connection c, all of 'the resistance R the contact'd, the lowerfend of the arm 0 to the contact -e, thence through the terminal f, the top contact g, the magnetic switch M,

held closed by the action of the winding on the switch f fI0II1 the switch 'M through thf contact 71., the trolley wire 1', the armature A,

the trolley wire 7c,"the trminal'tnpthe contact-plate n, the. upper end of the controller arm C, the contacto, the whole of the re- 4 5'0 sistanceRE-the terminal the trolley wirer,

t etrolle wire 8, to

athe minus side of'theiswitch' Current the fingers v and m.

remain bridged, the winding will hold the will also flow from the wire a through the winding t of the switch M, the trolley wire a,

the finger v, the contact ring w, and the fin- 55 ger ac to trolley wires and thence to the negative side of the switch K. The latter circuit is maintained as long as the disk in bridges As long as these fingers switch M closed, and as long as-the switch M remains closed the motor circuit will be closed. a As soon as the hoisting'mechanism turns the switch L enough to cause the circuit to open. at the finger v, the coil 15 will be denergized and the switch M will automatically open, breaking the motor circuit.

In Fi s. 4 and 5 I have shown the form of switch'fi, which I prefer, in connection with a hoisting mechanism. The electric motor '1 7o drives the hoisting-drum 2, to whose shaft is connected in any desired manner the worm shaft 3, driving the worm-Wheel 4. The shaft5 of the latter carries the disk 'w, having a ring of conducting material with the notch 7 5 6 therein. To the bottom of the notch is pivoted the trigger 7 which is connected by the spring 8 to the disk. The contact-fingers v and a: have their-ends spaced apart, but both rest on the contact ring 11) except where they are opposite the notch 6. As the ung w nears its limit of travel, the ends of the fingers engage the outer-end of the trig er 7 and pull the same against the side 0 the notch against the force of the spring 8.

When the end of the'trigger passes the ends of the contact fingers, the trigger instantly flies to the opposite side of the notch, break-.

ing the circuit between the fingers, quickly,

and thus preventing injurious arcing and the 0 burning of the said fin ers.

To lower the load,'1;t i's only necessary to move the controller arm C to the down position when the motor circuitfis established as follows: from the plus side of the switch 9 K through the wire a, the terminal g, the "contaot'b, the cross connection 0, the resistance R the contact 0, the lower end-of the controller arm 0, the contactlaten, the

terminal m, the trolley wire ic, t e armature 10o A, the trolley .wire 7', to the point i. As the switch M is op'en,-the current passes from the point '5 through the terminal: y, the contactplate 2, the upper end of the controller arm 0,

. "down position:

the contact (1, the cross-connection b, the resistance R the contact 1), its terminal q, the trolley wire r, the field F, and the trolley wire 8 to the minus side of the switch. he motor connections are thus complete but the current passes through the armature A in a direction the reverse of what it did when the arm 0 was on the up position, causing a reverse rotation of the motor and thelowering of the load. After the motor has rotated the disk to a short distance in a direction opposite the arrow, the disk to will bridge the fingers v and x, which will complete the circuit of the switch coil t and close the motor circuit at g.

Referring now to Fig. 2, the parts are the same except that the switch m is arrange in one position to connect the terminals m and m and in the opposite position to connect the terminals f and y; that the contact plate a is divided into two sections n and n connected res ectively to the terminals m and m; that t ere is the switch a to connect the switch M to the terminal m; and that the wire running from the switch M may be connected at will by the switch a with the point i, or the trolley wire is. If the parts are as shown on Fig. '2 except that the switch a connects the trolley wire 3' to'the point t, and if the arm C is moved to the up position, the circuits will be precisely as in Fig. 1 when the arm C thereon is in the uposition. When the arm C is thrownto the down osition, the circuits are the same as in Fig. 1,

the plate a taking the place of the plate n. If the switch m be made to connect the terminals f and y, the switch a be closed, and

the switch a be closed on the upper contact, thus connecting the bottom of the switch M with the trolley-wire k, the circuits will be as follows when the arm O is thrown to the from the plus side of the switch K through the wire a, the terminal q, the contact I), the resistance R the contact 0, the lower end of the arm C, the plate M, the terminal m, the switch a the switch M (supposing the same to have been closed) the switch a", the trolley wire 7c, the armature A, the trolley wire 3', the terminal y, the: plate 2, the upper end of the arm C, the contact al the resistance R wire 1', the field F and the trolley-wire s to the minus side of the switch K. The circuit of the coil tis as in Fig. 1. The switch L being properly set, the switch M will be opened when the load reached the limit of its descent.

Referring now to Fig. 3, a second limit switch L and a second circuit breaker switch M have been added, the coil t having its positive end connected to the positive feedwire of the coil 25. The remaining end ofthe cexii t is joined to an extra trolley wire 4b which leads to the limit switch L, the switche" L and L having a common return the terminal q, the trolleythrough the trolley wire 8. When the controller arm is thrown to the up position, the contacts 4) and 90 being bridged and the switch M closed, the circuits are as follows: from the plus side of the switch K through the terminal q, the resistance R, the lower end of the arm C, the late 6, the switch M, the armature A, the ate a, the up er end of the arm 0, the resistance R and t e field F to the minus side of the switch K. The current through the coil t asses from the positive wire a through the finger v, the ring w and the finger a: to the trolley wire 3 and the negative feed wire. When the ring rotates so that it no longer bridges the fingers o and 00, the switchM is opened as in Fig 1. As the switches L and L are preferably on the same shaft, the circuits through the coil and the switch L are closed and opened simultaneously with that in the coil t and the switch L. The switches M and M operate simultaneously also, though there is current through only one at a time. When the arm C is thrown to the down position, the currents will be as in the down osition in Fig. 2, the circuits through the coils t and t and the switches L and L remaining unchanged.

It will be noticed that the system herein described has several im ortant advantages, among which are the following: The circuit breaker or magnetic switch M is entirely automatic in its action; does not require manipulation by hand; has no small mechanical latches, fingers or other parts'subject to disarrangement; and has no overload coils or other device requiring calibration or adjustment. The limit switch L is simple, has few parts and is entirely dust and weather proof. It is small and has a rather large range of capacity and gear reduction and can generally be attached to some shaft or gear in almostany geared mechanism to give the desired limit of travel, without changing the speed reduction with which it was originally equip in quantities instead of being made up special for each particular geared mechanism. The arrangement of circuits and the design of the apparatus is such that when the motor circuit is once opened it is only necessary to reversecontroller arm to reestablish the motor circuit in the opposite direction to continue the o eration of the machine. sary or the operator to close by hand the circuit breaker, thus avoidin confusion to the operation and accident to t e machine. readily seen that if it were necessary to close circuit breaker by hand. the operator mi ht do so before he had reversed'the controlFer; themachine wouldthen continue to run in the same direction as before which would probably result in an accident to the machine. 4 4 I, v I am aware that circuit opening devices It is unnecesped. This allows it to be manufactured Itis'- disastrous Wreckmay occur.

have been constructed in which the circuit breaker is opened by energizing an electromagnetic tripping device. ref]: It should be noted that in my arrangement the main circuit is opened, not by energizing an electro-magnet, but by opening the circuit of the electro-magnet t and I consider this construction possesses valuable advantages. In the movable open-circuit'ed arrangement above mentioned, if any of the connections to the tripping coil become opened during the action of the hoist it will fail to act when the limit of the travel is reached and a l/Vith my arrangement if any of the connections to the coil t become opened the switch M will at .once open, cutting off power from the motor till the defect is remedied.

I elairn 1. A motion-limiting device for motordriven machinery, embracing a reversing controller, a limit switch and means for includingthe said switch'in the motor circuit in one direction of motion, and for bypassing the switch when'the controller is reversed.

2. A motion-limiting device for motordriven machinery, embracing a reversing controller, a limit switch, and means for opening the same automatically when the limit of I when the controller is actuated in the reverse direction, the said switch being automatically closed by the reverse motion of the driven machinery.

4. In a system of control for electric motors, the combination of a reversing controller, an electro-magnet, a limit switch in the motor circuit normally held in a closed position by the electro-magnet, a'second switch actuated by a driven member for openin the circuit of said electroagnet when the iimit of travel in one direction is reached, and means for bypassing said limit switch when said controller is reversed.

Signed at McKeesport, Pa, this 9th day of Oct. 1906.

GEORGE BAEHR. Witnesses:

W. B. FELL, CORA LENHART. 

